The present invention relates to an apparatus for aligning a polygon or other optical device relative to a base so that the polygon can be removed from the base and remounted on similar bases without requiring realignment.
Various kinds of apparatus are known for adjusting and mounting optical devices. For example, U.S. PAT. NO. 4,496,416, issued Jan. 29, 1985 relates to method and apparatus for adjusting and mounting optical components in optical instruments. The apparatus and method of this patent relates to positioning of an optical component relative to other portions of an instrument, and then after adjustment is completed rigidly attaching the instrument to the optical device in a permanent manner. For example, an optical element can be adjusted and firmly mounted in place in a telescope using the method and apparatus of this patent.
The method and apparatus disclosed in U.S. PAT. No. 4,496,416 requires an optical element to be adjusted with respect to a particular instrument and then an adhesive bonds the element to the instrument. If the optical element needs to be replaced, the procedure would have to be repeated. Thus, the method and apparatus of this patent does not enable an optical instrument or portions thereof to be replaced in the field without realigment and positioning of the element.
U.S. PAT. NO. 4,537,827, issued Aug. 27, 1985 relates to an optically flat semiconductor base plate structure. More specifically, the patent discloses a silicon wafer being mounted on a base plate for inclusion in an optical device, such as a liquid crystal light valve. An optically flat surface presses the silicon wafer toward a base plate and against an o-ring seal surrounding a fluid adhesive, and the fluid adhesive hydrostatically distributes the force of compression to guarantee optical flatness and self-compensation for the amount of fluid adhesive surrounded by the o-ring.
The apparatus of U.S. Pat. No. 4,537,827 is designed to produce an optically flat element and utilizes hydrostatic pressure to hold the semiconductor device flat while the adhesive cures. The need to produce optically flat devices increases the cost of the fixture and requires the application of hydrostatic forces. The ring which holds the adhesive in place can expand in a radial direction when the element is pressed flat to compensate for excess adhesive. Thus, the outer diameter of the device varies as a function of the quantity of adhesive. The resulting variation in diameter of the device may be acceptable in the manufacture of a semiconductor device, but can present a problem in an alignment apparatus where relative dimensions between certain parts needs to be controlled.
Laser printers and other optical devices require precise positioning of optical elements, such as a rotatable polygon having multi-faceted reflecting mirrored surfaces in order to achieve the accuracy and quality required for laser printers. Such optical systems can be assembled and precisely aligned to each printer as it is produced. However, if subsequent replacement of the polygon is required then the entire alignment operation must be repeated, and such is difficult to achieve at a customer's location. While small printers may be easily transported to a repair facility, many printers incorporating laser optical systems are quite large and it is inconvenient and expensive to transport the entire printer to a repair facility. This, there is a need to align an optical device, such as a polygon, prior to its installation in a printer on the like so that the aligned optical device can be mounted in the printer during assembly of the printer, or later during repair or replacement of the optical device while obtaining precise positioning of the device in the printer.